1. Field of the Invention
The present invention relates to methods and apparatus for drilling with top drive systems. Particularly, the invention relates to methods and apparatus for retrieving a downhole tool through a top drive system. More particularly still, the invention relates to running a wireline through the top drive system to retrieve the downhole tool and running a wireline access below the top drive system. The invention also relates to performing a cementing operation with the top drive system.
2. Description of the Related Art
One conventional method to complete a well includes drilling to a first designated depth with a drill bit on a drill string. Then, the drill string is removed, and a first string of casing is run into the wellbore and set in the drilled out portion of the wellbore. Cement is circulated into the annulus behind the casing string and allowed to cure. Next, the well is drilled to a second designated depth, and a second string of casing, or liner, is run into the drilled out portion of the wellbore. The second string is set at a depth such that the upper portion of the second string of casing overlaps the lower portion of the first string of casing. The second string is then fixed, or “hung” off of the existing casing by the use of slips which utilize slip members and cones to wedgingly fix the second string of casing in the wellbore. The second casing string is then cemented. This process is typically repeated with additional casing strings until the well has been drilled to a desired depth. Therefore, two run-ins into the wellbore are required per casing string to set the casing into the wellbore.
As more casing strings are set in the wellbore, the casing strings become progressively smaller in diameter in order to fit within the previous casing string. In a drilling operation, the drill bit for drilling to the next predetermined depth must thus become progressively smaller as the diameter of each casing string decreases in order to fit within the previous casing string. Therefore, multiple drill bits of different sizes are ordinarily necessary for drilling in well completion operations.
Another method of performing well completion operations involves drilling with casing, as opposed to the first method of drilling and then setting the casing. In this method, the casing string is run into the wellbore along with a drill bit for drilling the subsequent, smaller diameter hole located in the interior of the existing casing string. The drill bit is operated by rotation of the drill string from the surface of the wellbore, and/or rotation of a downhole motor. Once the borehole is formed, the attached casing string may be cemented in the borehole. The drill bit is either removed or destroyed by the drilling of a subsequent borehole. The subsequent borehole may be drilled by a second working string comprising a second drill bit disposed at the end of a second casing that is of sufficient size to line the wall of the borehole formed. The second drill bit should be smaller than the first drill bit so that it fits within the existing casing string. In this respect, this method typically requires only one run into the wellbore per casing string that is set into the wellbore.
In some operations, the drill shoe disposed at the lower end of the casing is designed to be drilled through by the subsequent casing string. However, retrievable drill bits and drilling assemblies have been developed to reduce the cost of the drilling operation. These drilling assemblies are equipped with a latch that is operable to selectively attach the drilling assembly to the casing. In this respect, the drilling assembly may be preserved for subsequent drilling operations.
It is known in the industry to use top drive systems to rotate the casing string and the drill shoe to form a borehole. Top drive systems are equipped with a motor to provide torque for rotating the drilling string. Most existing top drives use a threaded crossover adapter to connect to the casing. This is because the quill of the top drive is not sized to connect with the threads of the casing.
More recently, top drive adapters has been developed to facilitate the casing running process. Top drive adapters that grip the external portion of the casing are generally known as torque heads, while adapters that grip the internal portion of the casing are generally known as spears. An exemplary torque head is disclosed in U.S. patent application Ser. No. 10/850,347, entitled Casing Running Head, which application was filed on May 20, 2004 by the same inventor of the present application. An exemplary spear is disclosed in U.S. Patent Application Publication No. 2005/0051343, by Pietras, et al. These applications are assigned to the assignee of the present application and are herein incorporated by reference in their entirety.
One of the challenges of drilling with casing is the retrieval of the drilling assembly. For example, the drilling operation may be temporarily stopped to repair or replace the drilling assembly. In such instances, a wireline may be used to retrieve the latch and the drilling assembly. However, many existing top drives are not equipped with an access for the insertion or removal of the wireline, thereby making the run-in of the wireline more difficult and time consuming. Additionally, during the temporary stoppage to retrieve the drilling assembly, fluid circulation and casing movement is also typically stopped. As a result, the casing in the wellbore may become stuck, thereby hindering the rotation and advancement of the casing upon restart of the drilling operation.
There is a need, therefore, for methods and apparatus for retrieving the drilling assembly during and after drilling operations. There is also a need for apparatus and method for fluid circulation during the drilling assembly retrieval process. There is a further need for apparatus and methods for running a wireline while drilling with casing using a top drive. There is yet a further need for methods and apparatus for accessing the interior of a casing string connected to a top drive.